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headertftp

How to handle unknown-length header (TFTP related)

It is probably relevant to other questions too. I need to build a simple TFTP server in C (octet mode only) that will work with most TFTP clients available today (I only need to implement the server).

opcode   //2 byte
filename // string (unknown size)
0        // 1 byte
mode     // string (unknows size, max 9 chars considering 'netascii')
0        // 1 byte

But I'm having a problem: the RRQ/WRQ packets have a unknown length field "filename" (and "mode"). Because my server needs to be generic, how can I implement this option? Create a ridiculously large buffer and wait until recvfrom() returns 0?

Thanks!

Solution

  • make the buffer no much larger than the payload size of an Ethernet packet... with TFTP recvfrom won't return buffers larger than that...